Process of treating animal fibers and products thereof



Patented Mar. 25, 1947 PROCESS OF TREATING ANIMAL FIBERS AND PRODUCTS THEREOF Milton Harris, Bethesda, Md., and Wilbur I. Patterson, Chagrin Falls, Ohio, assignors to Textile Foundation, Washington, D. C., a corporation of the District of Columbia No Drawing. Application August 19, 1942, Serial No. 455,368

Claims.

Our invention relates to the treatment of ma: terials which contain keratin and more particularly to animal fibers of the epidermal type such as hair and wool. With greater particularity, the invention relates to such materials which contain keratin and which are characterized by having a plurality of disulfide (or cystine) linkages in the molecule. This invention also relates to the product produced by the treatment which will be hereinafter described.

This application is a continuation in part of our copending application, Serial No. 336,312, filed May 20, 1940.

It is known that wool and hair and the like fibrous materials which contain keratin are subject to attack by insects such as moths and are likewise subject to shrinkage when subjected to treatment by hot water or steam, particularly when the water has been made alkaline as by the addition of soap. Attempts have been made to reduce thesusceptibility of such materials to attack by moths by various chemical treatments, generally the surface treatment of the fibers with chemicals known to be repugnant to moths or suspected of being toxic towards moths and their larvae. Other types of treatment have been resorted to such as fumigating the fibers or fabrics made therefrom, with camphor, naphthalene or halogen derivatives of aromatic compounds.

None of these types of treatment have, so far as we are aware, been successful in permanently mothproofing animal fibers, such as hair and wool or the fabrics made therefrom, to such an extent as to resist repeated washing or dry cleaning.

Attempts have been made to reduce or eliminate the shrinkage and felting tendency of such animal fibers by subjecting the fibers to chemical treatment with either oxidizing or reducing agents. treatments which have been heretofore attempted have resulted in reducingthe natural shrinkage of animal fibers to any marked degree without leaving the molecule and particularly the sulfur thereof in a highly reactive form which renders it more susceptible to damage and degradation in service.-

Our invention has for one of its objects the treatment of animal fibers of the epidermal type which contain keratin and which are characterized by having a plurality of disulfide (or cystine) linkages in the molecule, in a series of easily controlled and readily duplicated steps to produce a modified animal fiber which is resist- So far as we are aware, none of the- 2 tion of such a modified animal fiber which is resistant to both moths and felting, with a permanency not hitherto attained.

In one of its broad aspects, our invention con-' templates the treatment of animal fibers of the epidermal type as well as materials fabricated partially or completely therefrom by subjecting the material, which contains keratin and which is characterized by having a plurality of disulfide (or cystine) linkages in the molecule, to the action of a reducing agent while controlling the pH value of the reaction. This treatment disrupts some, or all, or a predetermined proportion of the disulfide groups of the cystine in the molecule and converts the said disulfide groups into sulfhydryl groups. is then reacted with an agent which contains a substituent reactive with the hydrogen. of the sulfhydryl group to form a substituted mmether in which the substit'uent may be an alkyl ant to moths and which is resistant to felting.

nucleus, an aralkyl nucleus, a substituted alkyl nucleus or a substituted aralkyl nucleus. There results from this novel treatment a novel product which we have found to be resistant to moths and resistant to felting.

The following example given by way of illustration discloses one manner in which our novel process may be employed. A given amount of wool was immersed in such a volume of approximately 0.3 M thioglycolic acid solution, which had been brought to pH 6 by. NaOH, that the molar ratio of thioglycolic acid to the disulfide room temperature i. e. 20 to 30 C. for twentyhours. The wool was then removed from the solution, washed with water to remove the excess thioglyeolic acid; and the washed wool was then placed in an aqueous solution having a pH of about 7.5 to 8.0. A convenient way of adjusting the pH is by means of a bulfer solution of any well-known type, the amount and strength of the solution being so adjusted that the acid formed in the ensuing reaction will not reduce the hydrogen ion concentration of the reaction medium below pH 7.5. Methyl iodide, CHJI, was added to the reaction mixture and agitated to insure thorough contact between the methyl iodide and the reduced wool. The treatment with the methyl iodide was continued until a sample of the wool, when treated with nitroprusside reagent, failed to give a positive test for the sulfhydryl group. The modified wool was then removed from the reaction bath, washed thoroughly with water and dried in the air. The

The so-treated material wool subjected to this treatment had had its disulfide groups or cystine linkages disrupted and converted into methyl substituted thio-ethers.'

Analysis of the untreated, i. e. original, wool showed a cystine' content of 12% while the cystine content of the modified wool produced by this illustrative example was the method of analysis in both instances being the cystine content analysis of Sullivan, Public Health Reports 86 (1930), and Research Paper RP 810,

Journal of Research of the National Bureau of Standards, vol. 15, 1935.

' The process illustrated in the above example may be subjected to many variations. Hereto- .fore it was believed that strongly alkaline solutions of thioglycolic acid were required for the reduction of the disulfide groups of wool to sulfhydryl groups because neutral and slightly acid solutions of thioglycolic acid do not dissolve the wool. It was assumed that dissolution of the treatment, as well as the concentration of the reducing agent, we have found it possible to effect the reduction of the disulfide or crystine linkages at hydrogen ionconcentrations between pH 0.0 and pH 12.0, without substantial dissolution or degradation of the wool. Nevertheless, it hasbeen found that with an alkalinity above about pH 9 there will be undesirable side reactions and an undesired amount of dissolving of the fiber in an alkaline reducing bath of this degree of alkalinity. Since it is desired to perform the process of this application with a minimum amount of undesired side reactions and a minimum amount of degradation of the animal fiber to be treated, it is preferred to carry out the reducing step at a hydrogen ion concentration below about pH 9. It has also been found that the undesired side reactions and undesired solution are minimized to a far more satisfactory extent bycarrying out the reducing step of the process in a neutral or acid medium preferably below pH '7 and more desirably atabout pH 5.

During the alkylation step of our process, we prefer to maintain the hydrogen ion concentration at a pH of between about 7.5 and about 8.0, as determined in aqueous media. We have found that alkylation may be satisfactorily accomplished under hydrogen ion concentrations between about pH 7.0 and about pH 9.0, provided dueprecautions are taken with regard to temperature, concentration of reagents and other operating conditions.

- It has been found in developing the invention described in this application that reducing agents such as mercaptan acids, for example thioglycglic acid, mercaptans, for example H28 or NaSH, more particularly alkyl mercaptans, such as butyl or, ethyl mercaptans and mercaptan glycols, such as beta-mercapto ethanol, are unique in their ability to reduce animal fibers, such as wool, without causing undesired solution or degradation under'the conditions of reduction. 7

The reduction can be performed with a solution of the reducing agent in an anhydrous solvent, as a solution of thioglycolic acid in alcohol or benzene or other non-aqueous solvent.

In the illustrative example we have described the reducing step as being performed'at room temperature and over a period of about twentyfour hours. Lower temperatures may be employed and longer periods of exposure to the reducing agent, if desired; or higher temperatures may be employed while shortening the period of exposure of the wool to the reducing agent. We prefer, however, to operate within a temperature range of between about 25 C. and about 50 C. and we prefer to expose the wool to the action of the reducing agent for a period of time between 30 minutes and twenty-four hours. The temperature employed and the length of exposure to the reducing agent will vary, depending upon whether we wish to effect a complete or partial reduction of all of the disulfide (or crystine) linkages. We may, if desired, subject the wool to the action of the reducing agent under such conditions and forsuch a period of time as to effect the reduction of, for example, 25% or 50% or more or less, of the disulfide (or crystlne) linkages.

The concentration of the reducing agent is of importance. It has been found desirable to use at all times a considerable excess of the amount of reducing agent over and above that theoretically necessary to reduce all the disulfide (crystine) linkages of the molecule. Itis preferred to use at least20 times the amount of reducing agent theoretically necessary. It has been determined that the amount of reduction increased rapidly with some increase in the concentration of the reducing agent. Thus, there was a noticeable rapid increase when the reducing agent was increased from 0.01' M to 0.2 M. There was an increase, although a less marked one, between 0.2 M and 0.5 M. Increase in the concentration beyond 0.5 M had relatively less effect. V

In preparing for and accomplishing the alkylating step so as to effect the substitution of the sulfhydryl hydrogens with alkyl or other nuclei, we may adjust the hydrogen ion concentration in any well-known manner as by means of a buffer solution. As a buffering agent we may use borax, soda ash, phosphate buffers and the like.

- As alkylating agents a wide variety of compounds may be employed: alkyl compounds, substituted alkyl compounds, aralkyl compounds or substituted aralkyl compounds. Some aryl compounds have been found by us to be reactive. As examples of compounds which we have tested and found to be effective as alkylating agents are:

Methyl iodide, CHaI Ethyl bromide, CsHsB! Allyl chloride, CH2=CHCH2C1 Benzyl chloride, CaH-sCHzCl Chloroacetone, ClCHzCOCHa Chloroacetic acid, ClCHzCOOH Diazomethane, CHzNz p-Nitrofluorobenzene, NOPO-J p-Nitroiodobenzene, NO -I It will be observed that the compounds given above by way of illustration fall under groups such as alkyl halides, which may be either-saturated or unsaturated, aralkyl halides, substituted aliphatic compounds in which one or more hydrogens have been replaced by nitrogen or oxygen and halogenated aromatic compounds. All of the compoundsjhowever, are characterized'by having in the molecule a substituent which will react with the hydrogen of the sulfhydryl groups formed by disrupting the disulflde linkages of the wool. We have found that the alkylating step of our process and the completeness of reaction may be controlled by changing the solvent medium employed during the alkylating step. We have found an aqueous medium, particularly one which contains a buffering agent, to be very effective in this stage of our process, especially when the alkylating reagent is normally liquid, We have also found that an alcoholic solution, containing, for example, ammonia, or other soluble basic reagent, is an efilcient medium for the alkylating step. We may, however, employ other suitably inert solvents such as benzol, toluol, methyl alcohol, ethyl alcohol, propyl alcohol, cyclohexane, aliphatic liquid hydrocarbons and mixtures thereof, such as naphtha, in carrying out the alkylating step.

Moreover, we have ascertained that the use of a liquid medium is not in all cases necessary in the successful performance of the alkylation. With suitable alkylating agents, possessing the requisite volatility, the alkylation stepmay be carried out with gaseous or vaporized reagents.

wool illustrated in this specification may be employed on wool fibers, wool yarn, wool cloth, piece goods or unfabricated wool in the bulk. While we have used wool as a representative example of the epidermal type of animal fiber to which our invention relates, other keratin-containing and epidermal type fibers and materials fabricated therefrom may be treated by our process.

We have found that representative wool may have a cystine content as great as 12%. ducing such wool by our process, we may convert practically all of the disulflde groups or cystine content into substituted thio-ethers by reduction and alkylation in accordance with our invention. The product of such complete reduction and alkylation we have found to be a new and valuable product. We may likewise effect a partial reduction and subsequent partial alkylation so as to leave a desired portion, for example, between 4 and 8%, of the cystine unchanged. We have found that better resistance to moths (than unmodified wool) is demonstrated when our modified wool contains between about 4% and about 8% of cystine, the remainder of the cystine having been converted to substituted thio-ethers. We have found that where the cystine of wool has been converted to substituted thio-ethers by our invention, the modified wool 'is much more resistant to felting .than natural wool. We find this result increases as the cystine content is decreased to 8% cystine and below.

While we do not wish to be bound by any theory which we may advance, it is our belief, based upon our knowledge of wool and upon its reported In re--.

molecular structure, that wool and all other animal fibers of the epidermal type which contain formula:

in which X and X are identical or substantially 7 similar side chain complexes containing C, H, N and 0, i. e. X and X represent the portions of the wool molecule to which the disulfidelinkages are attached, and a is a number greater than 1. The'reduction step of our process affects the disruption of the disulflde linkages, i. e, cystine, and forms cysteine, i. e. sulfhydryl, groups. Consequently, after the reduction step, that is, after the disruption of the disulflde linkages, the wool molecule may be represented as follows:

(II) x -s s-)x' (a i in which X and X are as in (I) above and represent the portions of the wool molecule to which the now disrupted disulflde linkages are attached, and a is a number greater than 1.

The alkylating step of our process accomplishes the replacement of the hydrogen of th sulfhydryl groups of the reduced wool with the selected nucleus. Thus, where methyl iodide or benzyl chloride is used as the alkylating agent, the final product will be:

(III) x -s s- )x' x -s s- )X' 01 41E: JJH: q HiCtHt HICEB respectively.

This may be more broadly stated as:

where R represents an alkyl, a substituted alkyl, an aralkyl ora substituted aralkyl nucleus, and a is a number greater than 1.

Where the wool has been but partially reduced,

i. e. part only of the disulflde linkages have been disrupted and converted to substituted thioethers, the molecule may [be represented as:

x[ -s s- }x' (it).

where R represents an alkyl, a substituted alkyl, an aralkyl, or a substituted aralkyl nucleus, and b and c are numbers the sum of which equals the number a which is greater than 1.

Having now described our invention in such manner that the nature of our invention may be understood and the invention may be practiced by others, we declare that what we claimis:

1. W001 fiber, characterized by resistance to moths and felting, in which at'least about onethird of the disulflde linkages of the wool molecule have been disrupted and changed to thioethers of the type in which X and X* represent portions of the f wool molecule to which the disrupted disulflde linkages are attached and R is selected from the group consisting of substituted and unsubstituted alkyl radicals.

2. Wool fiber, characterized [by resistance to moths and felting, in which at least about onethird of the disulflde linkages ,of \the wool molecule have been disrupted and" changed to thioethers of the type in which X and X represent portions of the wool molecule to which the disrupted disulfide linkages are attached and R is an alkyl radical.

3. The process 01 treating wool to render it resistant to moths and felting which comprises subjecting the wool to the action of a reducing agent selected from the group consisting of lower alkyl mercaptans, .thioglycolic acid and betamercaptoethanol while maintaining the pH of the reaction below about pH 9 until at least about one-third of the disulflde linkages of the wool have been converted to sulfhydryl groups,

pH '7 and pH 9 with a compound selected from the group consisting of substituted and unsubstituted alkyl monohalides to convert the sulfhydryl group into thioethers.

4. The process of treating wool to render it resistant to moths and felting which comprises subjecting the wool to the action of thioglycolic acid while maintaining the pH of the reaction below about pH 9 until at least about one-third of the disulphide linkages of the wool have been converted to sulfhydryl groups, then treating the wool at a pH between about pH 7 and pH 9 with a compound selected from the group consisting of substituted and unsubstituted alkyl monohallides to convert the sulfhydryl group into thioet ers.

then treating the wool at a pH between about 5. The process of treating wool to render it resistant to moths and felting which comprises subjecting the wool to the action oi. beta-mercaptoethanol while maintaining the pH of the reaction below about pH 9 until at least about one-third of the disulflde linkages oi the wool have been converted tosulihydryl groups, then treating the wool at a pH between about pH 7 and pH 9 with a compound selected from the 10 group consisting of substituted and unsubstituted alkyl monohalides to convert the sulfhydryl group into thioethers. MILTON HARRIS.

WILBUR I PATTERSON.

REFERENCES CITED The following references are of record the file of this patent:

UNITED STATES PATENTS Number OTHER REFERENCES Michaelis, "A Study of Keratin," Jr. American Leather Chemists Assn., vol. 30, 1935, pages 561- 568.

Pillemer et al., Specificity of Kerateine De- 30 rivatives, Proceedings of the Soc. for Exp. Biol- 

